The present invention relates to a solid electrolyte usable in batteries, capacitors, electrochromic devices, sensors, etc.
Solid electrolytes are produced, for example, by mixing an acryloyl-modified polymer compound having an alkylene oxide polymer chain, an electrolytic salt and, optionally, a solvent, in which mixture the polymer compound is crosslinked.
For crosslinking the polymer compound, employable are any among the following: UV irradiation, electronic irradiation, thermal crosslinking and the like, which, however, have the following drawbacks.
In a cell system containing a solid electrolyte, the solid electrolyte acting as a binder shall be also in the positive electrode and the negative electrode, wherein active materials are employed. For the solid electrolyte in such a cell system, UV irradiation is often problematic in that UV rays cannot readily penetrate into the cell system because of the existence of active materials. As a result, the polymer compound constituting the solid electrolyte is often difficult to crosslink through such UV irradiation to a satisfactory degree.
Polymer crosslinking through electronic irradiation may be possible even in such a cell system, as the transmittance of electron rays through the system is high. However, satisfactory polymer crosslinking is difficult in thick cell systems even through electronic irradiation. In addition, another problem with electronic irradiation is that the apparatus for it is expensive.
Conventional thermal crosslinking requires heating at high temperatures of 90.degree. C. or higher, and is therefore problematic in that it often causes degradation of electrolytic salts and much vaporization of solvents, if used.
In that situation, some improved methods for producing solid electrolytes have been proposed in JP-A 5-36305, 5-114419 and 5-151992, which, however, are still defective in the following points. In the method in JP-A 5-36305, a radical polymerization accelerator or retardant is used so as to control the curing rate of polymers, and the amount thereof to be added to the polymer system must be controlled extremely accurately. The method in JP-A 5-114419 and 5-151992 is characterized in that two solutions, either one of which contains an alkali metal salt, are mixed and cured in cells, and therefore the application range of the method is limited.
The invention has been made in consideration of the problems noted above. Namely, the object of the invention is to provide a solid electrolyte obtained by employing a specific crosslinking initiator in order to solve the above-identified problems.